CARIES MECHANISMS: This research is designed to establish the composition of the solution within the incipient caries lesion as a function of (1) the properties of the solution outside the tooth, and (2) the permselective character of the tooth surface. CARIES PREVENTION: Substances are sought which change the permselective properties of the tooth surface in a direction that will inhibit caries formation. FLUORIDE STUDIES: The nature of the reaction of F- with the surfaces of hydroxyapatite crystals is being investigated to identify the basic structural and thermodynamic variables controlling the reaction. Phase diagrams are being calculated for various models of solubility behavior of Ca5(PO4)3OH-Ca5(PO4)3F solid solutions. ETCHING TECHNIQUES: Solution compositions are being investigated which will produce "adhesive" etched enamel surfaces with minimal loss of enamel. Procedures for fluoridating etched surfaces without destroying the adhesive character are also under investigation. REMINERALIZATION SOLUTIONS; Slurries that will be effective, and practicable remineralizers of tooth surfaces are being tested. BIBLIOGRAPHIC REFERENCES: Brown, W.E., Patel, P.R. and Chow, L.C. Formation of CaHPO4 2H2O from Enamel Mineral and Its Relationship to Caries Mechanism. J. Dent. Res. 54:475-481, May-June 1975. Patel, P.R. and Brown, W.E. Thermodynamic Solubility Product of Human Tooth Enamel: Powdered Sample. J. Dent. Res. 54:728-736, 1975.